Sign text display method and apparatus for vehicle navigation system

Abstract

In a vehicle navigation system, an improvement in the way sign text data is displayed. Sign text data stored in the system corresponds to road signs and is displayed for route guidance purposes. Along certain types of road segments, for instance freeway ramps where there are multiple signs in sequence and each sign is associated with a decision point at which the driver must decide which direction to take, a comparison is made between the content (the sign text) of the first sign and the last sign in the sequence. If any words or phrases coincide, only the content of the last sign is displayed at the point of the first sign. This simplifies the displayed sign text and provides better and more concise route guidance to the driver.

I claim: 
     
       1. In a navigation system, a method of indicating to a user a route on a road network, the road network including a plurality of road segments connecting at intersections, the method comprising the steps of: assigning a decision point to each of selected intersections;   storing guiding data associated with each decision point, the guiding data indicating a guided route at the associated decision point;   for a guided route including a plurality of road segments, retrieving the guiding data associated with all decision points along the guided route;   comparing the guiding data associated with a current decision point along the guided route to the guiding data associated with a last decision point along the guided route; and   if at least a portion of the compared guiding data coincides, providing to the user only the guiding data associated with the last decision point.   
     
     
       2. The method of claim 1, wherein the step of providing includes visually displaying the guiding data. 
     
     
       3. The guidance method of claim 1, wherein the step of providing includes audibly announcing the guiding data. 
     
     
       4. The method of claim 1, wherein the coinciding portion of the guiding data is a phrase. 
     
     
       5. The method of claim 1, wherein the coinciding portion of the guiding data is at least a word. 
     
     
       6. The method of claim 1, wherein the guiding data is a sign text. 
     
     
       7. The method of claim 1, wherein the guiding date is identical to a text of a road sign near the decision point. 
     
     
       8. The method of claim 1, wherein the guiding data is an edited version of a text of a road sign near the decision point. 
     
     
       9. The method of claim 1, wherein the guided route is at least in part along a ramp. 
     
     
       10. The method of claim 9, wherein the ramp connects a limited access highway to a street. 
     
     
       11. The method of claim 9, wherein the ramp connects two streets. 
     
     
       12. The method of claim 1, wherein the step of providing occurs prior to the current decision point. 
     
     
       13. The method of claim 1, wherein the step of providing occurs near a decision point intermediate of a first and the last decision points. 
     
     
       14. The method of claim 1, wherein a coinciding portion of the guiding data is one of at least a word and a phrase, and further comprising the steps of: first determining if the coinciding portion of the data is a phrase; and   second determining if the coinciding portion is not a phrase and is at least a word.   
     
     
       15. The method of claim 1, wherein the ramp connects two limited access highways. 
     
     
       16. The method of claim 1, further comprising determining if the route includes a ramp, and performing the step of retrieving only if the route includes a ramp. 
     
     
       17. The method of claim 1, further comprising the step of deleting a selected portion of the guiding data associated with the last decision point, prior to the step of providing. 
     
     
       18. A navigation system for indicating to a user a route on a road network, the road network including a plurality of road segments connecting at intersections, the system comprising: means for assigning a decision point to each of selected intersections;   a memory storing guiding data associated with each decision point, the guiding data indicating a guided route at the associated decision point;   means for retrieving from the memory the guiding data associated with all decision points along the guided route, for a guided route including a plurality of road segments;   means for comparing the guiding data associated with a current decision point along the guided route to guiding data associated with a last decision point along the guided route; and   means for providing to the user only the guiding data associated with the last decision point if at least a portion of the compared guiding data coincides.   
     
     
       19. The system of claim 18, wherein the means for providing includes a visual display. 
     
     
       20. The system of claim 18 wherein the means for providing includes means for audibly announcing. 
     
     
       21. The system of claim 18 wherein the coinciding portion of the data is a phrase. 
     
     
       22. The system of claim 18, wherein the coinciding portion of the data is at least a word. 
     
     
       23. The system of claim 18, wherein the guiding data is a sign text. 
     
     
       24. The system of claim 18, wherein the guiding data is identical to a text of a road sign near the decision point. 
     
     
       25. The system of claim 18, wherein the guiding data is an edited version of a text of a road sign near the decision point. 
     
     
       26. The system of claim 18, wherein the guided route is at least in part along a highway ramp. 
     
     
       27. The system of claim 26, wherein the ramp connects a limited access highway to a street. 
     
     
       28. The system of claim 26, wherein the ramp connects two limited access highways. 
     
     
       29. The system of claim 26, wherein the ramp connects two streets. 
     
     
       30. The system of claim 18, wherein the means for providing operates prior to the current decision point. 
     
     
       31. The system of claim 18, wherein the means for providing operates near a decision point intermediate of a first and last decision points. 
     
     
       32. The system of claim 18, further comprising means for determining if the route includes a ramp, and means for performing the step of retrieving only if the route includes a ramp. 
     
     
       33. The system of claim 18, further comprising means for deleting a selected portion of the guiding data associated with the last decision point before it is provided to the user. 
     
     
       34. A computer-readable memory containing program instructions for indicating to a user of a navigation system a route on a road network, the road network including a plurality of road segments connecting at intersections, the instructions comprising: assigning a decision point to each of selected intersections;   storing guiding data associated with each decision point, the guiding data indicating a guided route at the associated decision point;   for a guided route including a plurality of road segments, retrieving the guiding data associated with all decision points along the guided route;   comparing the guiding data associated with a current decision point along the guided route to the guiding data associated with a last decision point along the guided route; and   if at least a portion of the compared guiding data coincides, providing to the user only the guiding data associated with the last decision point.   
     
     
       35. A computer-implemented navigation system for indicating to a user a route on a road network, the road network including a plurality of road segments connecting at intersections, the system comprising: means for assigning a decision point to each of selected intersections;   a memory storing guiding data associated with each decision point, the guiding data indicating a guided route at the associated decision point;   means for retrieving from the memory the guiding data associated with all decision points along the guided route, for a guided route including a plurality of road segments;   means for comparing the guiding data associated with a current decision point along the guided route to guiding data associated with a last decision point along the guided route; and   means for providing to the user only the guiding data associated with the last decision point if at least a portion of the compared guiding data coincides.